Conventionally, as a technique for ejecting microdroplets, a technique regarding head drive voltage control for an ink jet printer has been reported (refer to Japanese Patent Application Laid-Open No. 2003-211671 and No. H11-240148). In addition, as a technique for a direct current power supply device, a technique regarding a battery simulator for referring to set and recorded characteristics to control output voltage has been reported (refer to Japanese Patent Application Laid-Open No. H11-064462).